The present invention relates generally to an apparatus and method of manufacturing a resin structure reinforced with long fibers and, more particularly, to an apparatus and method of manufacturing for a single-step in-line compounding of a reinforcing fiber with extrusion compression molding.
Elongated resin structures reinforced with fibers in which thermoplastic resins are reinforced with continuous fibers have mechanical properties superior to those structures reinforced with short fibers. Such structures are beneficial because they can be cut and formed into pellets or similar materials. Elongated thermoplastic resin structures reinforced with fibers are generally manufactured by the so-called pultrusion method by impregnating a thermoplastic resin into a continuous reinforcement fiber bundle while the bundle is passed through a cross-head extrusion die, after which the resin-impregnated fiber bundle is drawn out through a die. After undergoing the pultrusion method, the structures are cut to a desired size.
Other processes are used to produce elongated thermoplastic resin structures reinforced with fiber, for example, where first the plastic is melted in a long single screw extruder which is fed to another single screw extruder. Next chopped strands are fed into the melt, and the reinforcing fiber melt is pumped into an accumulator after which the required log size is cut and fed into a vertical molding press.
Currently, there is no apparatus available employing a single-step process that utilizes a single screw extruder as a reinforcing fiber compounder and melt deposition unit. Likewise, there is no method currently available where reinforcing fibers are fed into a barrel of the apparatus such that the fibers are constantly maintained in a stretched condition regardless of the movement of the apparatus, thereby eliminating the possibility of fiber entanglement.
It is, therefore desirable to provide an apparatus and process for in-line compounding of reinforcing fiber and molding in a single-step process. A reinforcing product is compounded by use of a reciprocating single screw extruder having a reinforcing fiber compounder and a melt depositing unit, where the reinforcing fibers are severed at a maximum desirable length and kept in a stretched tensioned condition regardless of the apparatus positioning such that there are no loose or sagging fibers during the process.
Advantageously, the in-line compounding/extrusion apparatus of the present invention allows for the in-line compounding of reinforcing fibers with extrusion compression molding in a single step by utilizing a reciprocating single screw injection unit. Typically, the in-line compounding of reinforcing fibers with extrusion compression molding would involve high cost, bulky equipment consisting of combinations of single screw, twin screw and plunger deposition assemblies. By using a single-step process for the in-line compounding of reinforcing fibers and extrusion compression molding, the present invention offers a more cost effective method of producing a higher quality part.
In accordance with the preferred embodiment of the present invention, there is provided a method to incorporate the continuous reinforcing fiber into the reciprocating single screw injection unit and to sever and uniformly impregnate the fine filaments with resin keeping maximum fiber length in the part.
In accordance with another aspect of the preferred embodiment of the present invention the apparatus includes winding/unwinding reels and guides which prevent the reinforcing fibers from sagging and breaking during a melt deposition step or during forward and rear movement of the reciprocating single screw injection unit.
The above and other objects and advantages of the invention will be apparent from the following description, the accompanying drawings and the appended claims.